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SOHO Status Report - May 2006

22 May 2006 11:41

Mission Status

The spacecraft status is nominal, with the High Gain Antenna (HGA) Z-axis in a fixed position. On 7 March a nominal manoeuvre (station keeping and momentum management) was performed and 0.0146 kg of fuel was used. The remaining hydrazine is 118 kg. The solar array degradation after 123 months of flight is 18.25%, which corresponds to 1.78% per year.

The NASA Sun-Solar System Connections Senior Review Panel ranked SOHO in the excellent category for science merit, and in the compelling category for relevance to S3C goals. The Panel recommended continued funding for SOHO through FY 2010, though with slightly reduced funding (6%, 12%, and 7% less than the proposed budget in fiscal years 2007, 2008, and 2009, respectively). In response to the Panel's recommendation to lower the operational cost of SOHO, work has begun on automating SOHO operations. The aim is to move to unmanned night passes in the summer of 2007. This will also require changes to the on-board software.

Operations and Archiving

All instruments are nominal and SOHO science operations are progressing smoothly. UVCS' O VI detector has developed symptoms similar to that of the SUMER A detector: counts from a few pixel rows appear to be collected in an adjacent pixel row. The similarities in the symptoms and in the detector designs for SUMER and UVCS point to a common root cause, which is under investigation. The primary suspect at this stage is accumulated radiation damage to the analog-to-digital converters (ADCs) of the crossed delay-line (XDL) detectors.

Links to the SOHO archives (including mirrors) are accessible at http://soho.esac.esa.int/data/.

Science Highlights

Scientists developed a theoretical model for solar cycle strength prediction, based on a calibrated flux-transport dynamo model. They predict that the next solar cycle will have a 30 - 50% higher peak than the current cycle. Taking into account recent MDI measurements of a decelerating meridional flow, they also predict that the next solar cycle will only start in late 2007 or early 2008, six to twelve months later than the current NOAA Space Environment Center prediction.

The MDI team has made significant improvements to their holographic far-side imaging technique. The original method only allowed for seeing the central regions of the Sun's far side, about one quarter of its total area. With the new and improved method, one can see the entire far side, including the poles. Images and movies are available at: http://soi.stanford.edu/data/full_farside/.

Using coordinated observations with CDS, EIT, MDI and the VLA, scientists have measured coronal magnetic field strengths of 1750 G at a height of 6000 km and 960 G at 12 000 km above a pair of large sunspots. This is the first time that radio brightness temperatures as large as 106 K have been observed in a 15 GHz solar radio source above the limb. The field strength measurements yield a magnetic scale height of 7000 km.

During the total solar eclipse of 29 March SOHO supported several expedition teams with special observations.